If you do the sim on the classic, the base training on the classic then do a NG diffs course, you get 737 300-900 on the ticket.
If you did all NG sim, you will need to do an NG to classic diffs course.
Usually TRTOs that " leave you to sort it out" are selling courses cheap and the sting in the tail, as you will find, will be the base training.
As a guide, you will need 6 landings and I would budget for 1 hr in the A/c, between 6 and 8000 euro.
Try Sabenavita at Vilnius, speak to Darius:
Good luck